In recent years, a technique to epitaxially grow a Si-based crystal such as a SiGe crystal, etc., on a Si-based substrate or a Si-based crystal layer is often used for fabricating a semiconductor device.
For example, in a technique described in JP-A-2006-13428, by epitaxially growing a SiGe crystal having a lattice constant larger than that of a Si crystal at a position sandwiching a channel region of a p-type transistor, a compressive stress is generated in the channel region and thereby straining the channel region. As a result, it is possible to improve carrier (hole) mobility in the channel region, thereby improving an operating speed of the p-type transistor.
Moreover, in the fabricating method of the SiGe based bipolar transistor, there is a well known technique to epitaxially grow a SiGe crystal after removal of a native oxide film on a Si substrate in a hydrogen gas atmosphere. The technique is, for example, described in JP-A-2006-13428. According to this technique, it is possible to grow SiGe crystal with good crystallinity on the Si substrate.
However, at the stage of growing the SiGe crystal, when there are comparatively a lot of members made of silicon nitride such as a mask material etc. on the Si substrate, silicon nitrides dispersed from the material may adhere to area used for a base of growth of the SiGe crystal on the Si substrate, which may disturb the growth of the SiGe crystal with good crystallinity.